Heat sink

ABSTRACT

Example embodiments may provide a heat sink capable of cooling even when hot spots generate a large amount of heat that is unevenly distributed in some regions of a heating element package. The heat sink may include a plurality of heat pipes including one end portions thermally connected to a heating element package provided with a heating element in a package and other end portions thermally connected to a heat dissipation unit, in which the plurality of heat pipes includes at least a first heat pipe and a second heat pipe having greater heat transport capacity than heat transport capacity of the first heat pipe.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of International Patent Application No. PCT/JP2018/047979 filed on Dec. 26, 2018, which claims the benefit of Japanese Patent Application No. 2017-254601, filed on Dec. 28, 2017. The contents of these applications are incorporated herein by reference in their entirety.

BACKGROUND Technical Field

The present disclosure relates to a heat sink configured to transport heat from a heating element to radiator fins via heat pipes to thereby cool the heating element.

Background

As electronic apparatuses are provided with increasingly higher functions, a plurality of heating elements such as electronic parts may be mounted in a heating element package in the electronic apparatuses. Furthermore, amounts of heat generated by the respective electronic parts are also becoming diversified depending on differences in functions of the electronic parts or the like. Therefore, hot spots with high amounts of heat generated may be unevenly distributed in some regions of the heating element package. In order to reliably and efficiently cool even such a heating element package, a plurality of heat pipes may be thermally connected to the heating element package.

As a heat sink in which a plurality of heat pipes are thermally connected to a heating element, for example, a heat sink provided with a projection is proposed in which the projection separates at least one heat pipe near the heating element, among a plurality of heat pipes, from the heating element in a thickness direction of a heat receiving plate compared to the other heat pipes (Japanese Patent Application Laid-Open No. 2014-126249). According to Japanese Patent Application Laid-Open No. 2014-126249, providing the projection that separates at least one heat pipe near the heating element in the thickness direction of the heat receiving plate compared to the other heat pipes equalizes distances of the one heat pipe and the other heat pipes from the heat source. This reduces a heat load on the one heat pipe, and can thereby efficiently cool the heating element.

On the other hand, according to Japanese Patent Application Laid-Open No. 2014-126249, since heat transport capacity of the plurality of heat pipes are substantially the same, distances of the one heat pipe and the other heat pipe from the heat source are equalized. Therefore, regarding heat pipes directly above the heat source, these heat pipes are separated from the heating element in the thickness direction of the heat receiving plate, and so there has been room for further exerting the heat transport capacity by bringing the heat pipes closer to the heat source. Therefore, there has been room for improving cooling performance of the heat sink.

Furthermore, when the heat transport capacity of the plurality of heat pipes are substantially uniform, it is necessary to identify specifications of the other heat pipes according to the heat transport capacity required for the heat pipes directly above the heat source. An example of heat pipes having large heat transport capacity is a heat pipe with a specification of a large diameter. On the other hand, the heat pipe having a large diameter has large thermal resistance, demonstrates poor workability such as bending, and has difficulty achieving proper positioning, thus leaving room for improving heat transport characteristics.

SUMMARY

The present disclosure is related to providing a heat sink capable of displaying excellent cooling performance even when hot spots generating a large amount of heat are unevenly distributed in some regions of a heating element package.

One aspect of the present disclosure is a heat sink provided with a plurality of heat pipes, each of which includes one end portion thermally connected to a heating element package provided with a heating element in a package and another end portion thermally connected to a heat dissipation unit, in which the plurality of heat pipes include at least a first heat pipe and a second heat pipe having greater heat transport capacity than the first heat pipe.

Another aspect of the present disclosure is a heat sink provided with a plurality of heat pipes, each of which includes a central portion thermally connected to a heating element package provided with a heating element in a package and both end portions thermally connected to a heat dissipation unit, in which the plurality of heat pipes include at least a first heat pipe and a second heat pipe having greater heat transport capacity than the first heat pipe.

A further aspect of the present disclosure is the heat sink, in which the one end portions of the plurality of heat pipes are disposed in parallel along an extending direction of the heating element package.

A still further aspect of the present disclosure is the heat sink, in which the central portions of the plurality of heat pipes are disposed in parallel along an extending direction of the heating element package.

A still further aspect of the present disclosure is the heat sink, in which the heat transport capacity of the second heat pipe is greater than the heat transport capacity of the first heat pipe due to a difference in dimension in traverse directions of the heat pipes, a difference in shapes in traverse directions of the heat pipes, and/or a difference in a wick structure accommodated in the heat pipes.

A still further aspect of the present disclosure is the heat sink, in which the one end portions of the plurality of heat pipes are thermally connected to a heat receiving plate and the heat receiving plate is thermally connected to the heating element package.

A still further aspect of the present disclosure is the heat sink, in which the central portions of the plurality of heat pipes are thermally connected to the heat receiving plate and the heat receiving plate is thermally connected to the heating element package.

A still further aspect of the present disclosure is a heat sink for cooling the heating element package in which the heating element in plurality is disposed in the extending direction of the package.

A still further aspect of the present disclosure is the heat sink, in which one end portion of the second heat pipe is thermally connected to a position of the heating element.

A still further aspect of the present disclosure is the heat sink, in which a central portion of the second heat pipe is thermally connected to a position of the heating element.

A still further aspect of the present disclosure is the heat sink for cooling the heating element package including a hot spot generating a large amount of heat in the extending direction of the package. Note that the term “hot spot of the package” means a region exhibiting a higher temperature than an average temperature of the heating element package surface among all the package surfaces in the present Description.

A still further aspect of the present disclosure is the heat sink, in which one end portion of the second heat pipe is thermally connected to the hot spots.

A still further aspect of the present disclosure is the heat sink, in which a central portion of the second heat pipe is thermally connected to the hot spot.

According to one aspect of the present disclosure, at least the first heat pipe and the second heat pipe having greater heat transport capacity than the first heat pipe are used together, and so if hot spots of the heating element package and the heating element are thermally connected closer to the second heat pipe than the first heat pipe, it is possible to exert excellent cooling performance with respect to the heating element package with the greater heat transport capacity of the second heat pipe. Moreover, even if hot spots are present in the heating element package, by thermally connecting the hot spots in the region of the second heat pipe, it is possible to efficiently cool the hot spots because of relatively greater heat transport capacity of the second heat pipe. Furthermore, since the first heat pipe is also thermally connected to the heat dissipation unit, the first heat pipe can also contribute to heat transportation, reduce a load on the second heat pipe, and as a result, can provide excellent cooling performance for the heating element package.

According to another aspect of the present disclosure, the one end portions or the central portions of the plurality of heat pipes are disposed in parallel along the extending direction of the heating element package, and it is thereby possible to reliably and easily thermally connect the second heat pipe to the hot spot and the heating element of the heating element package.

According to a further aspect of the present disclosure, the one end portions or central portions of the heat pipes are thermally connected to the heat receiving plate, and so thermal connectability between the heat pipes and the heating element package improves. The heat receiving plate also acts as a heat equalizing plate that equalizes heat loads on the respective heat pipes disposed in parallel, whereas because of the presence of the second heat pipe having greater heat transport capacity, it is not necessary to consider the action as the heat equalizing plate to be as important as used to be, and the heat receiving plate can be made thinner. Therefore, it is possible to reduce the weight and the size of the heat sink.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat sink according to a first embodiment of the present disclosure.

FIG. 2 is a plan view of the heat sink according to the first embodiment of the present disclosure.

FIG. 3 is a side view of one end portion of the heat sink according to the first embodiment of the present disclosure.

FIG. 4 is a side view of one end portion of a heat sink according to a second embodiment of the present disclosure.

FIG. 5 is a side view of one end portion of a heat sink according to a third embodiment of the present disclosure.

FIG. 6A is a plan view of a heat sink according to a fourth embodiment of the present disclosure, FIG. 6B is a side view of the heat sink according to the fourth embodiment of the present disclosure and FIG. 6C is an A-A cross-sectional view of the heat sink according to the fourth embodiment of the present disclosure.

FIGS. 7A, 7B and 7C are explanatory diagrams of a heat sink according to another embodiment of the present disclosure.

FIGS. 8A, 8B and 8C are explanatory diagrams of a heat sink according to a further embodiment of the present disclosure.

FIGS. 9A, 9B and 9C are explanatory diagrams of a heat sink according to a still further embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, a heat sink according to a first embodiment of the present disclosure will be described with reference to the accompanying drawings. As shown in FIGS. 1 to 3, a heat sink 1 according to the first embodiment is provided with a first heat pipe 11 thermally connected to a heating element package 100 provided with a heating element 101 in a package 102, a second heat pipe 21 likewise thermally connected to the heating element package 100 provided with the heating element 101 in the package 102, and a heat dissipation unit 40 including a plurality of radiator fins 41 to which the first heat pipe 11 and the second heat pipe 21 are commonly thermally connected. The heating element package 100 is a cooling target of the heat sink 1. The first heat pipe 11 and the second heat pipe 21 are heat transport members, inner spaces of which are sealed and which are subjected to decompression processing.

One end portion 12 of the first heat pipe 11 is thermally connected to the heating element package 100 and another end portion 13 is thermally connected to the heat dissipation unit 40. One end portion 22 of the second heat pipe 21 is thermally connected to the heating element package 100 and another end portion 23 is thermally connected to the heat dissipation unit 40.

The heat sink 1 is provided with a plurality of heat pipes composed of a plurality of (two heat pipes in FIGS. 1 to 3) first heat pipes 11 and a plurality of (two heat pipes in FIGS. 1 to 3) second heat pipes 21 (hereinafter, a plurality of heat pipes including the first heat pipes and the second heat pipes may be referred to as “heat pipe group”). In the heat pipe group, the respective heat pipes are disposed in parallel in a side view. In the heat sink 1, the respective heat pipes are disposed in parallel in a row in a side view. In the heat pipe group, the second heat pipes 21 are disposed at the center in a side view and the first heat pipes 11 are disposed at both ends in a side view. More specifically, the two first heat pipes 11 and the two second heat pipes 21 are disposed in parallel, the two second heat pipes 21 are disposed at the center, and one first heat pipe 11 is disposed at each of both ends.

The one end portion 12 of the first heat pipe 11 is thermally connected to a first surface 31 of a heat receiving plate 30. The one end portion 22 of the second heat pipe 21 is thermally connected to the first surface 31 of the heat receiving plate 30. The first heat pipe 11 and the second heat pipe 21 are disposed on the same surface as the surface of the heat receiving plate 30. The heating element package 100 is thermally connected to a second surface 32, which is a surface of the heat receiving plate 30 opposite to the first surface 31. Therefore, the first heat pipe 11 and the second heat pipe 21 are thermally connected to the heating element package 100 via the heat receiving plate 30. Note that in the heat sink 1, a cover member 110 is attached so as to cover top surfaces of the heat receiving plate 30, the one end portion 12 of the first heat pipe 11 and the one end portion 22 of the second heat pipe 21.

A cross-sectional shape in a direction orthogonal to a longitudinal direction of the first heat pipe 11 at the one end portion 12 of the first heat pipe 11 (that is, a traverse direction of the first heat pipe 11) is not particularly limited and is a circular shape in the heat sink 1. That is, in the heat sink 1, the cross-sectional shape of the first heat pipe 11 in the direction orthogonal to the heat transport direction is a circular shape. A cross-sectional shape in a direction orthogonal to a longitudinal direction of the second heat pipe 21 at the one end portion 22 of the second heat pipe 21 (that is, a traverse direction of the second heat pipe 21) is not particularly limited and is a circular shape just like the first heat pipe 11 in the heat sink 1. That is, in the heat sink 1, the cross-sectional shape of the second heat pipe 21 in the direction orthogonal to the heat transport direction is a circular shape. Therefore, the cross-sectional shape in the traverse direction of the one end portion 12 of the first heat pipe 11 is substantially the same as the cross-sectional shape in the traverse direction of the one end portion 22 of the second heat pipe 21. Note that the “longitudinal direction of the heat pipe” in the present Description means a heat transport direction of the heat pipe and the “traverse direction of the heat pipe” means a direction orthogonal to the heat transport direction of the heat pipe.

A wick structure (not shown) for causing a working fluid (not shown) in a liquid phase to circulate from the other end portion 13, 23 to the one end portion 12, 22 is accommodated in the first heat pipe 11 and the second heat pipe 21. The wick structure is a structure having a capillary force. In the heat sink 1, the wick structure of the first heat pipe 11 is the same as the wick structure of the second heat pipe 21.

A diameter (outer diameter ϕ2) in the traverse direction of the one end portion 22 of the second heat pipe 21 is greater than a diameter (outer diameter ϕ1) in the traverse direction of the one end portion 12 of the first heat pipe 11. That is, the first heat pipe 11 and the second heat pipe 21 are heat pipes having structures differing in that both heat pipes are different in diameter in the traverse direction. Since the diameter (outer diameter ϕ2) in the traverse direction of the one end portion 22 is greater than the diameter (outer diameter ϕ1) in the traverse direction of the one end portion 12, the second heat pipe 21 exhibits greater heat transport capacity than the first heat pipe 11. In the heat sink 1, the shape and diameter in the traverse direction of the first heat pipe 11 are substantially the same from the one end portion 12 to the other end portion 13, and the shape and diameter in the traverse direction of the second heat pipe 21 are substantially the same from the one end portion 22 to the other end portion 23.

A ratio (outer diameter ϕ2/outer diameter ϕ1) of the diameter (outer diameter ϕ2) in the traverse direction of the one end portion 22 to the diameter (outer diameter ϕ1) in the traverse direction of the one end portion 12 is not particularly limited as long as it exceeds 1.00 and it is, for example, preferable to be 1.05 to 3.00, more preferable to be 1.10 to 2.00 and particularly preferable to be 1.20 to 1.50. When the outer diameter ϕ2/outer diameter 1 is smaller than 1.05, the difference in heat transport capacity between the first heat pipe 11 and the second heat pipe 21 is small, it tends to be impossible to dispose the second heat pipe 21 having sufficiently high heat transport capacity in the hot spots. On the other hand, when outer diameter ϕ2/outer diameter ϕ1 is greater than 3.00, the difference in constraint between bending of the first heat pipe 11 and bending of the second heat pipe 21 increases, and it tends to be difficult to use the heat pipes as components in the one heat sink. A ratio of the cross-sectional area in the traverse direction of the one end portion 22 to the cross-sectional area in the traverse direction of the one end portion 12 is not particularly limited as long as it exceeds 1.00 and it is, for example, preferable to be 1.1 to 9.0, more preferable to be 1.2 to 4.0 and particularly preferable to be 1.4 to 2.2.

The diameter (outer diameter ϕ2) in the traverse direction of the one end portion 22 is not particularly limited as long as it is greater than the diameter (outer diameter ϕ1) in the traverse direction of the one end portion 12, and the diameter (outer diameter ϕ1) in the traverse direction of the one end portion 12 is, for example, 5.0 mm to 10 mm. The diameter (outer diameter 2) in the traverse direction of the one end portion 22 is, for example, 5.3 mm to 30 mm.

The one end portion 12 of the first heat pipe 11 and the one end portion 22 of the second heat pipe 21 are disposed in parallel along the extending direction of the heating element package 100. Furthermore, the one end portion 12 of the first heat pipe 11 and the one end portion 22 of the second heat pipe 21 are disposed on substantially the same plane. Therefore, the thickness of the heat receiving plate 30 directly below the one end portion 12 of the first heat pipe 11 is substantially the same as the thickness of the heat receiving plate 30 directly below the one end portion 22 of the second heat pipe 21. Note that the “extending direction of the package” in the present Description means the direction along the package surface connected to the heat sink among the outer surfaces of the package.

As shown in FIG. 2, the shape of the one end portion 12 in a plan view of the first heat pipe 11 is substantially linear and the shape of the central portion 14 in a plan view disposed between the one end portion 12 and the other end portion 13 is also substantially linear. The shape of the one end portion 22 in a plan view of the second heat pipe 21 is substantially linear and the shape of the central portion 24 in a plan view disposed between the one end portion 22 and the other end portion 23 is also substantially linear. Therefore, the first heat pipes 11 and the second heat pipes 21 are substantially linear regions in a plan view disposed side by side over a range from the one end portion 12, 22 to the central portion 14, 24.

In the heat sink 1, a bent portion 15 is formed at the other end portion 13 of the first heat pipe 11 thermally connected to the heat dissipation unit 40. Therefore, all the first heat pipes 11 are substantially L-shaped in a plan view. The bent portion 15 of the one first heat pipe 11 on the right side is bent rightward, whereas the bent portion 15 of the one first heat pipe 11 on the left side is bent leftward. That is, the bending directions of the bent portions 15 are opposite between the first heat pipe 11 on the left and the first heat pipe 11 on the right.

A bent portion 25 is formed at the other end portion 23 of the second heat pipe 21 thermally connected to the heat dissipation unit 40. Therefore, all the second heat pipes 21 are substantially L-shaped in a plan view. The bent portion 25 of the one second heat pipe 21 on the right side is bent rightward, whereas the bent portion 25 of the one second heat pipe 21 on the left side is bent leftward. That is, the bending directions of the bent portions 25 are opposite between the second heat pipe 21 on the left and the second heat pipe 21 on the right. Note that since the first heat pipe 11 is smaller in diameter in the traverse direction than the second heat pipe 21, processing such as bending is performed more easily than processing on the second heat pipe 21. Therefore, processing can be performed as required so that the radius of curvature of the bent portion 15 of the first heat pipe 11 may be smaller than the radius of curvature of the bent portion 25 of the second heat pipe 21. As described above, the heat sink 1 allows heat to be uniformly transported to the entire heat dissipation unit 40 and heat dissipation efficiency is thereby improved.

With the bent portions 15 and 25, the first heat pipes 11 and the second heat pipes 21 are both configured so that the other end portions 13 and 23 extend in substantially parallel to the longitudinal direction of the heat dissipation unit 40. In the heat dissipation unit 40, radiator fins 41 are disposed in parallel so that main surfaces (flat portions) of the radiator fins 41 are disposed in substantially parallel to the extending directions of the one end portions 12 and 22 of the first heat pipes 11 and the second heat pipes 21. The radiator fins 41 are thin plate-shaped members. In the heat sink 1, both the other end portions 13 of the first heat pipes 11 extending parallel to the longitudinal direction of the heat dissipation unit 40 and the other end portions 23 of the second heat pipes 21 reach the end portions in the longitudinal direction of the heat dissipation unit 40.

As shown in FIG. 1, an appearance shape of the heat dissipation unit 40 is substantially rectangular parallelepiped. The heat dissipation unit 40 has a structure in which a first radiator fin group 42, an appearance shape of which is substantially rectangular parallelepiped and a second radiator fin group 43 adjacent to the first radiator fin group 42 and an appearance shape of which is substantially rectangular parallelepiped are stacked one on the other. Both the first radiator fin group 42 and the second radiator fin group 43 have a structure in which the plurality of radiator fins 41 attached to a plate-shaped support 45 are disposed in parallel to the longitudinal direction of the heat dissipation unit 40.

The other end portions 13 of the first heat pipes 11 and the other end portions 23 of the second heat pipes 21 are inserted between the first radiator fin group 42 and the second radiator fin group 43. With the other end portions 13 and 23 disposed between the first radiator fin group 42 and the second radiator fin group 43, the heat dissipation unit 40, the first heat pipes 11 and the second heat pipes 21 are thermally connected.

The material of containers used for the first heat pipes 11 and the second heat pipes 21 is not particularly limited, and examples of the material include copper, copper alloy, aluminum, aluminum alloy, stainless steel. A working fluid to be sealed into the containers can be selected as appropriate according to adaptability with the container material, and examples of the working fluid include water, fluorocarbon, cyclopentane, ethylene glycol or a mixture of these substances.

The wick structure accommodated in the containers is not particularly limited and examples of the wick structure include sintered body of metal powder of copper, copper alloy or the like, mesh made of metal wire such as copper or a copper alloy, braided body of metal such as copper or a copper alloy, non-woven fabric cloth made of resin component, thin grooves formed in an inner surface of containers. The material of the radiator fins 41 is not particularly limited and examples of the material include metal such as copper and a copper alloy.

Thereafter, an example of how to use the heat sink 1 according to the first embodiment will be described. As shown in FIG. 3, the heat pipe groups of the heat sink 1 are disposed such that the second heat pipes 21 are disposed directly above and in the vicinity of the heating element 101, which is a hot spot of the heat receiving plate 30 side planes of the heating element package 100. In FIG. 3, the heating element is located at a central portion in a side view of the heating element package 100. Accordingly, the second heat pipes 21 are disposed at the center in a side view of the heat pipe group and the first heat pipes 11 are disposed at both end portions in a side view of the heat pipe group. Therefore, the first heat pipes 11 are located far from the hot spot compared to the second heat pipes 21.

The heat generated in the heating element package 100 is transferred to the heat receiving plate 30. The heat transferred to the heat receiving plate 30 is transferred from the heat receiving plate 30 to the one end portions 12 of the first heat pipes 11 and the one end portions 22 of the second heat pipes 21. The heat transferred to the one end portions 12 of the first heat pipes 11 is transported from the one end portions 12 of the first heat pipes 11 to the other end portions 13 of the first heat pipes 11 by heat transport action of the first heat pipes 11. The heat transferred to the one end portions 22 of the second heat pipes 21 is transported from the one end portions 22 of the second heat pipes 21 to the other end portions 23 of the second heat pipes 21 by heat transport action of the second heat pipes 21. The heat transported to the other end portions 13 of the first heat pipes 11 and the heat transported to the other end portions 23 of the second heat pipes 21 are transferred to the heat dissipation unit 40 having the plurality of radiator fins 41. The heat transferred to the heat dissipation unit 40 is released from the heat dissipation unit 40 to an outside environment, and it is thereby possible to cool the heating element 101 housed in the heating element package 100.

At this time, since the second heat pipes 21 having greater heat transport capacity than the first heat pipes 11 are disposed directly above and in the vicinity of the heating element 101, which is a hot spot of the heating element package 100, the large heat transport capacity of the second heat pipes 21 makes it possible to exert excellent cooling performance on the hot spot of the heating element package 100. Therefore, even when a hot spot is generated in the heating element package 100, it is possible to exert excellent cooling performance for the entire heating element package. Since the first heat pipes 11 are also thermally connected to the heating element package 100, the first heat pipes 11 can contribute to heat transport of the heat pipe group. Therefore, the heat transport capacity of the first heat pipes 11 alleviates the loads on the second heat pipes and can exert cooling performance on the hot spot periphery of the heating element package 100. As a result, the heat sink 1 can exert excellent cooling performance for the entire heating element package 100.

In the heat sink 1, since the one end portions of the heat pipe group are disposed in parallel along the extending direction of the heating element package 100, it is possible to reliably and easily thermally connect the second heat pipes 21 to the region of the hot spot of the heating element package 100.

The heat receiving plate 30 also acts as a heat equalizing plate that makes uniform, a heat load on the heat pipe group disposed in parallel, but since the second heat pipes 21 having greater heat transport capacity are disposed at the hot spot, it is not necessary to consider the action as the heat equalizing plate as important as used to be, and as a result, the heat receiving plate 30 can be made thinner. Therefore, it is possible to reduce the weight and the size of the heat sink 1.

Thereafter, a heat sink according to a second embodiment of the present disclosure will be described using the accompanying drawings. Note that in the heat sink according to the second embodiment, the same components as the components of the heat sink according to the first embodiment will be described using the same reference numerals.

As described above, in the heat sink 1 according to the first embodiment, the plurality of first heat pipes 11 and the plurality of second heat pipes 21 are disposed in parallel in a side view, the second heat pipes 21 are disposed at the center and the first heat pipes 11 are disposed at both ends. Instead of this, in a heat sink 2 according to a second embodiment as shown in FIG. 4, all the second heat pipes 21 are disposed on one edge side in a side view and all the first heat pipes 11 are disposed on the other edge side in a side view.

In FIG. 4, the heating element 101 is disposed biased to one edge side (on the left half side in FIG. 4) of the package 102 in a side view and a hot spot of the heating element package 100 is formed biased to the one edge side. Accordingly, in the heat sink 2, both of the second heat pipes 21 having greater heat transport capacity than the first heat pipes 11 are disposed in parallel on the one edge side (left half side in FIG. 4) and both of the first heat pipes 11 are disposed in parallel on the other edge side (right half side in FIG. 4). In the heat sink 2, since the second heat pipes 21 having greater heat transport capacity than the first heat pipes 11 are disposed directly above and in the vicinity of the heating element 101, which is a hot spot of the heating element package 100, the greater heat transport capacity of the second heat pipes 21 allows excellent cooling performance to be exerted on the hot spot of the heating element package 100.

In the heat sink 2 as described above, even when the hot spot of the heating element package 100 is formed not at the central portion but biased to the edge part, it is possible to exert excellent cooling performance on the hot spot of the heating element package 100, and as a result, exert excellent cooling performance on the entire heating element package 100.

Thereafter, a heat sink according to a third embodiment of the present disclosure will be described using accompanying drawings. Note that in the heat sink according to the third embodiment, the same components as the components of the heat sink according to the first and second embodiments will be described using the same reference numerals.

In the heat sink 1 according to the first embodiment, the plurality of first heat pipes 11 and the plurality of second heat pipes 21 are disposed in parallel in a side view, the second heat pipes 21 are disposed at the center and the first heat pipes 11 are disposed at both ends. Instead, in a heat sink 3 according to the third embodiment as shown in FIG. 5, the second heat pipes 21 are disposed at both ends in a side view and the first heat pipes 11 are disposed at the center.

In FIG. 5, a plurality of (two in FIG. 5) heating elements 101 are accommodated in the package 102, and the heating elements 101 are disposed at both ends of the package 102 in a side view. Therefore, the hot spot of the heating element package 100 is formed of a plurality of (two in FIG. 5) parts separated apart at both ends. Accordingly, in the heat sink 3, the second heat pipes 21 having greater heat transport capacity than the first heat pipes 11 are disposed at both ends in a side view and the first heat pipes 11 are disposed at the center in a side view. In the heat sink 3, too, the second heat pipes 21 having greater heat transport capacity than the first heat pipes 11 are disposed directly above and in the vicinity of the heating elements 101, which are hot spots of the heating element package 100, and so the greater heat transport capacity of the second heat pipe 21 allows excellent cooling performance to be displayed on the hot spots of the heating element package 100.

As described above, even when a plurality of hot spots of the heating element package 100 are formed apart, the heat sink 3 can exert excellent cooling performance on the hot spots of the heating element package 100, and as a result, exert excellent cooling performance on the entire heating element package 100.

Thereafter, a heat sink according to a fourth embodiment of the present disclosure will be described using the accompanying drawings. Note that in the heat sink according to the fourth embodiment, the same components as the components of the heat sink according to the first to third embodiments will be described using the same reference numerals.

In the heat sink 1 according to the first embodiment, the one end portions 12 of the first heat pipes 11 and the one end portions 22 of the second heat pipes 21 are thermally connected to the heat receiving plate 30. Instead of this, as shown in FIGS. 6A and 6B, in a heat sink 4 according to the fourth embodiment, within a range of the heat receiving plate 30 from one end 33 to the other end 34, the first heat pipe 11 extends from the one end portion 12 to the other end portion 13, and the second heat pipe 21 extends from the one end portion 22 to the other end portion 23. Furthermore, as shown in FIGS. 6B and 6C, the first heat pipes 11 and the second heat pipes 21 are thermally connected to the first surface 31 of the heat receiving plate 30.

The radiator fins 41 are erected on the first surface 31 of the heat receiving plate 30. In the heat sink 4, the radiator fins 41 are erected on the first surface 31 of the heat receiving plate 30 in a vertical direction. Edge portions of the radiator fins 41 are attached to the first surface 31 of the heat receiving plate 30. As the heat dissipation unit 40, the plurality of radiator fins 41 are disposed in parallel at predetermined intervals from the one end 33 to the other end 34 of the heat receiving plate 30.

The heating element package 100 is thermally connected to a central portion 35 of the heat receiving plate 30 (that is, region other than the one end 33 and the other end 34 of the heat receiving plate 30). Therefore, a central portion 14 of the first heat pipe 11 (that is, region other than the one end portion 12 and the other end portion 13) and a central portion 24 of the second heat pipe 21 (that is, region other than the one end portion 22 and the other end portion 23) are thermally connected to the heating element package 100 and function as an evaporation unit. Furthermore, both end portions of the first heat pipe 11 (one end portion 12 and the other end portion 13) and both end portions of the second heat pipe 21 (one end portion 22 and the other end portion 23) are thermally connected to the heat dissipation unit 40 and function as a condensation unit.

Note that at the central portion 35 of the heat receiving plate 30 in the heat sink 4, some bends are formed in the first heat pipe 11 and the second heat pipe 21 so that the first heat pipe 11 and the second heat pipe 21 are drawn to the central portion in a direction orthogonal to the longitudinal directions of the first heat pipes 11 and the second heat pipes 21. The above-described aspect can improve thermal connectivity between the heat pipe group and the heating element package 100.

In the heat sink 4 in which the heating element package 100 is thermally connected to the central portion 14 of the first heat pipes 11 and the central portion 24 of the second heat pipes 21, greater heat transport capacity of the second heat pipes 21 allows excellent cooling performance to be exerted on the hot spot of the heating element package 100, and since the first heat pipes 11 are also thermally connected to the heating element package 100, the first heat pipes 11 can contribute to heat transport of the heat pipe group.

Thereafter, other embodiments of the present disclosure will be described. The same components as the components of the above-described respective embodiments will be described using the same reference numerals. In the heat sinks according to the above-described respective embodiments, heat transport capacity of the second heat pipes is greater than the heat transport capacity of the first heat pipes due to differences in dimension in the traverse direction between the heat pipes. Instead of this, as shown in FIGS. 7A, 7B and 7C and FIGS. 8A, 8B and 8C, heat transport capacity of the second heat pipes may be greater than heat transport capacity of the first heat pipes depending on differences in shapes in the traverse direction of the heat pipes.

In FIGS. 7A, 7B and 7C, a shape in the traverse direction of the first heat pipes 11 is a flat shape obtained by flattening a circle and a shape in the traverse direction of the second heat pipes 21 is a circular shape. Of the flat shape of the first heat pipes 11, one flat portion that forms the main surface is disposed on the lower side (heating element package 100 side). Since the shape in the traverse direction of the heat pipe is a circular shape, heat transport capacity improves compared to the heat pipe having a flat shape.

In FIGS. 8A, 8B and 8C, more heat pipes (second heat pipes 21) are thermally connected directly above the heating element 101, which is a hot spot, and this improves heat transport capacity of the heat pipes directly above the heating element 101 as the plurality of second heat pipes 21 as a whole. In FIGS. 8A, 8B and 8C, the shape in the traverse direction of the second heat pipes 21 is a flat shape and the shape in the traverse direction of the first heat pipes 11 is a circular shape. The surface in a thickness direction of the flat shape of the second heat pipes 21 is disposed on the underside (heating element package 100 side). Of the flat shape, the surface in the thickness direction is disposed on the heating element package 100 side, and it is thereby possible to thermally connect more heat pipes (second heat pipes 21) directly above the heating element 101 compared to the heat pipes, whose shape in the traverse direction is a circular shape.

As another embodiment of the present disclosure, both the shape in the traverse direction of the first heat pipes and the shape in the traverse direction of the second heat pipes may be flat shapes obtained by flattening a circular shape.

As variations of the wick structure, different types of the wick structure may be used for the first heat pipes and the second heat pipes from among a sintered body of metal powder, mesh made of metal wire, metal braided body, non-woven fabric cloth made of resin component and grooves or the like.

As shown in FIGS. 9A, 9B and 9C, by adopting different cross-sectional shapes of the wick structures in the traverse direction of the respective heat pipes for the first heat pipes 11 and the second heat pipes 21, heat transport capacity of the second heat pipes 21 may be made greater than heat transport capacity of the first heat pipes 11.

In FIGS. 9A, 9B and 9C, a sintered body of metal powder is used as the wick structure for both the first heat pipes 11 and the second heat pipes 21. For the first heat pipes 11, a wick structure 51 is formed in layers on an inner surface of the first heat pipes 11. For the second heat pipes 21, a wick structure 52 including a layered wick structure and two projections 53 projecting from the layered wick structure is formed on the inner surface of the second heat pipes 21. The projections 53 of the wick structure 52 are disposed so as to face each other. The wick structure 52 including the projections 53 has higher circular current characteristics of a working fluid in a liquid phase compared to the wick structure 51 without any projections 53, and as a result, heat transport capacity of the second heat pipes 21 is greater than heat transport capacity of the first heat pipes 11. Note that in FIGS. 9A, 9B and 9C, both the shape in the traverse direction of the first heat pipes 11 and the shape in the traverse direction of the second heat pipes 21 are circular shapes and both heat pipes have substantially the same cross-sectional area in the traverse direction.

In the heat sinks according to the above-described first to third embodiments, bent portions are formed at the other end portions of the first heat pipes and the other end portions of the second heat pipes, both the first heat pipes and the second heat pipes are substantially L-shaped in a plan view. However, the shapes of the first heat pipes and the second heat pipes in a plan view are not particularly limited, but may be, for example, substantially linear. In this case, the radiator fins may be disposed in parallel so that the main surfaces (flat portions) of the radiator fins are disposed in a direction substantially orthogonal to the extending direction of the one end portion of the heat pipes group.

In the heat sinks according to the above-described first to third embodiments, although the cross-sectional shapes in the traverse direction of the first heat pipes and the second heat pipes are circular shapes, the cross-sectional shapes in the traverse direction of the first heat pipes and the second heat pipes are not particularly limited, but may be flat shapes instead or may be an ellipse, a polygon such as a square, a rounded rectangle or the like.

Although the heat sinks according to the above-described embodiments are provided with the heat receiving plates, since second heat pipes having greater heat transport capacity are disposed in the hot spot, no heat receiving plate may be provided depending on usage. In the above-described respective embodiments, although the heat dissipation unit is constructed of a plurality of radiator fins, the heat dissipation unit is not particularly limited, but may be a water cooling jacket or the like.

The heat sink of the present disclosure can be used in extensive fields, and since the heat sink can exert excellent cooling performance even when hot spots generating a high amount of heat are unevenly distributed in some areas to be cooled, the heat sink of the present disclosure can be used in the field where high performance electronic parts such as a server used at a data center are used. 

What is claimed is:
 1. A heat sink comprising a plurality of heat pipes, each of which comprises one end portion thermally connected to a heating element package provided with a heating element in a package and another end portion thermally connected to a heat dissipation unit, wherein the plurality of heat pipes comprises at least a first heat pipe and a second heat pipe having greater heat transport capacity than the first heat pipe.
 2. A heat sink comprising a plurality of heat pipes, each of which comprises a central portion thermally connected to a heating element package provided with a heating element in a package and both end portions thermally connected to a heat dissipation unit, wherein the plurality of heat pipes comprises at least a first heat pipe and a second heat pipe having greater heat transport capacity than the first heat pipe.
 3. The heat sink according to claim 1, wherein one end portions of the plurality of heat pipes are disposed in parallel along an extending direction of the heating element package.
 4. The heat sink according to claim 2, wherein central portions of the plurality of heat pipes are disposed in parallel along an extending direction of the heating element package.
 5. The heat sink according to claim 1, wherein the heat transport capacity of the second heat pipe is greater than the heat transport capacity of the first heat pipe due to a difference in dimension in traverse directions of the first and second heat pipes, a difference in shapes in traverse directions of the first and second heat pipes, and/or a difference in a first wick structure accommodated in the first heat pipe and a second wick structure accommodated in the second heat pipe.
 6. The heat sink according to claim 2, wherein the heat transport capacity of the second heat pipe is greater than the heat transport capacity of the first heat pipe due to a difference in dimension in traverse directions of the first and second heat pipes, a difference in shapes in traverse directions of the first and second heat pipes, and/or a difference in a first wick structure accommodated in the first heat pipe and a second wick structure accommodated in the second heat pipe.
 7. The heat sink according to claim 1, wherein one end portions of the plurality of heat pipes are thermally connected to a heat receiving plate and the heat receiving plate is thermally connected to the heating element package.
 8. The heat sink according to claim 2, wherein central portions of the plurality of heat pipes are thermally connected to the heat receiving plate and the heat receiving plate is thermally connected to the heating element package.
 9. The heat sink according to claim 1, wherein the heat sink is for cooling the heating element package in which the heating element in plurality is disposed in an extending direction of the package.
 10. The heat sink according to claim 2, wherein the heat sink is for cooling the heating element package in which the heating element in plurality is disposed in an extending direction of the package.
 11. The heat sink according to claim 9, wherein one end portion of the second heat pipe is thermally connected to a position of the heating element.
 12. The heat sink according to claim 10, wherein a central portion of the second heat pipe is thermally connected to a position of the heating element.
 13. The heat sink according to claim 1, wherein the heat sink is for cooling the heating element package comprising a hot spot generating a large amount of heat in an extending direction of the package.
 14. The heat sink according to claim 2, wherein the heat sink is for cooling the heating element package comprising a hot spot generating a large amount of heat in an extending direction of the package.
 15. The heat sink according to claim 13, wherein one end portion of the second heat pipe is thermally connected to the hot spot.
 16. The heat sink according to claim 14, wherein a central portion of the second heat pipe is thermally connected to the hot spot. 